the next step
 

Hello everyone, I am looking to do the "next step" I want to build my motor and upgrade my turbo... I was planing on buying a jdm head and doing cams, valves springs and retainers. anyone know which set up would be recomended? also i want to build the bottom end. If anyone has any suggestions please let me know it would be very helpful. I plan on upgrading the turbo and getting it tuned all at the same time.
So what i am trying to get at is, what bottom end kit is good, what head kit is good, what turbo would be good, and still have my car everyday drove. when it is all done i am trailering my car to kingpin performance in Arizona to be tuned.
I know i have a lot of grammer errors, please just blame it on my age. thanks for the seccs time. please get back to me soon

OH snap! This is gonna get good.

:subscribes to thread:

What kind of goal do you have?

I would recommend calling Nate at Subaru Specialists in Sacramento (see the banner ad at the top of this page). He will be able to give you good advise to match your goals.

First, if you plan on keeping the car street legal and daily driveable, bottom end and head work is overkill. The stock bits are plenty good enough for streetable power. You can put down well over 300awhp w/o having to go to extremes. Once you start screwing w/ forged bits and headwork, you're not gonna have a streetable car, or if you do, you're probably wasting money on a lot of really expensive work.

However, if you're really looking to build the snot out of the motor, I wouldn't bother w/ "kits". You need to find a builder and give them you're needs and have them put together a parts list specific to your goals. Hell, at that level you're looking at $1000's for parts, so trying to find a "kit" isn't gonna save you any significant cash.

I'm not sure about bottom-end type stuff. I've heard that the stock STi bits are actually very stout... then I've heard that that's only for the earliest '04 STis that came off the line, and the more recent stuff isn't so good. You'll have to get someone more knowledgeable than I to help you there.

As far as heads... I would avoid the JDM heads unless you're building a track-only car, and even then that might not be much better than the US heads. Basically, the JDM heads have no TGV, so you'll have to have a JDM ECU that won't freak out over the missing sensor input since I don't believe anyone's come up w/ a software solution to get the USDM ECU to work w/o the TGV. And if you do that, pretty much kiss ever passing smog goodbye... I don't think the OBD-II test will pass on a JDM ECU... but I could be wrong.

Either way, I don't know that there are any real benefits to the JDM heads anyway. You can always put a TGV delete kit on the US heads (which will of course require the JDM ECU...) if you don't want the tumbler in there. Other than that, I think the heads are pretty much the same. The old reason to go to JDM heads was to get the AVCS, but US STi's already have variable timing.

In talking w/ Nate about headwork, he said he's got a guy that can really build up some hot heads. Port, polish, springs, retainers, and cams, plus blueprinting and balancing the bottom-end, and you're looking at a 9k redline. 'Course, that's like $3000 to $5000 for just the headwork alone.

Now, picking a turbo to match that monster is another thing I don't know too much about. Something like a GT30-12 might work on a 2.0L w/ all that work, but I'm not sure what to put on a 2.5L that's that hot. Whatever it is, it's probably *massive*, and in order to make boost out to that incredible redline, it will probably have a bunch of lag (well, reletively speaking). Nick (doubleurx) went from the stock VF39 on his tuned STi (that had retarded amounts of low-end grunt) to a GT30-10, and he says that the low-end feels just like stock now, which he likes because he drives it daily. Although now, when he gets on it and the turbo kicks in, the car is insanely fast and will spin tires in just about any gear.

In fact, I would talk to Nick about what he's done, since he's basically out at the far reaches of power w/o going to internals/heads. And, IMO his car is already too fast for the street. :lol:

Hope that helps!

Not to nitpick, but Nick is actually running a SBGT30-12.
The 10 is a better 2 liter turbo.

If you want to get crazy, you can go upt to something like a SBGT30-14, which is massive, or a GT35, which is just stupid big, but at that point you're building a track or drag car, as it won't spool until way after 4k and then will just make stupid amounts of power at high RPM's..........not a street motor.

Woops, I knew that... Scott B. has a GT30-10 on his STi and it's too small... it spools faster than the stock VF39, and doesn't make much more power.

I wonder how the GT30-10 does on a 2.0L...

I like this route : http://forums.nasioc.com/forums/showthread.php?t=773999:devil:

Yeah, but those numbers are on race gas and 93 octane :(
Nick's running the "medium" Slowboy turbo, and he's making 340 with a safe tune on 91......:D

It just boggles the mind what these little 4-banger motors are capable of w/ only bolt-ons!

I wonder what would happen if Subaru's next Impreza was a flat-6 3.6L turbo motor hatchback... Porsche killer much? :eek: Wait... damn those WRC rules!

Dude, imagine what that thing would do to World Challenge in a couple years when turbo engines take over. :p